Questions on the products' hardware, on the LEDs and different connection configurations

The calls recorded through an E1 interface stop on playback after approximately 30 to 60 seconds. According to the LEDs device has been connected properly. There is also an increased bit error rate. What could be the reason?

1. Bit Error Rate

An increased bit error rate could be caused by the way in which the EyeSDN USB-E1 device is connected, for example, if it is connected in parallel.

We therefore recommend the following methods of connection for the EyeSDN USB-E1:

  1. Insertion into the line using its own two RJ45 female connectors. This guarantees that the stub cable is kept short.
  2. Keep the stub cable as short as possible if using a patch panel. One to two meters long should be fine, but the shorter the better!
  3. Using a signal enhancer, or booster, and an additional terminator on the EyeSDN USB-E1. This enables distances of several hundred meters to be covered. If covering the distance between the PC and the connector is problematic, a USB extender can also be used as well as a booster (for distances up to 45m). This converts the USB cable to category 5 or category 6 and then a second adaptor at the end of the cable converts it back to a USB connector.

2. Interrupted Recordings

There are two possible reasons for interrupted recordings:

  • The first is bit errors that could cause a layer 1 resynchronization. This interrupts both the recording of the B channel and the updating of the D channel protocol.
  • The second is that the PC is too slow. If all 30 channels are occupied, the EyeSDN USB-E1 transmits 512 KB/s via the USB interface. This is equivalent to approximately 50% of the actual bandwidth available for bulk transfer. The PC must be able to continuously process this data rate. We recommend a processor with a clock frequency > 1.5 GHz.

The procedure for finding out which of these two causes is at the root of the problem is simple: record only one active call over the E1 interface. If the recording is still interrupted, then it's because of the bit error rate or the connection. Otherwise, we recommend you try a PC with different components.

The device's LEDs don't react, even though the software has been correctly installed?

Several seconds pass before the LEDs on the installed device react. This time is required to load certain firmware into the device. If the LEDs still aren't lit after approximately 30 seconds, then it could be due to one of the following:

  1. The hardware (the EyeSDN USB device) is not being recognized by the PC because the PC was unable to locate the driver during installation. This can be checked by opening the tab folder "Settings/Devices" in the Call Browser software. If the device's serial number does not appear there at the bottom then the driver must be reinstalled, as described in the "Driver Installation" chapter in the manual.
  2. Either the windows service or the computer was not restarted after the driver was installed, the device connected or changes made in the settings, meaning that none of these changes have yet come into effect. You may either close the Call Browser program and restart the computer or manually start the windows service for the recording software. This may be found in the "Using the Call Recording Service" chapter in the manual.
  3. If neither points 1 nor 2 have helped to solve the problem, then try using a different USB slot or, if you are using a USB hub, a different USB hub and then restart the windows service or the computer.
  4. The ISDN and USB cables provided with the device are not checked individually before packaging; although a rare occurance, it is possible that one of these cables may be defective. Please test the cables by exchanging them with others. If you have no extra cables available to use, please contact us.
  5. If none of the above has helped to solve the problem, please contact us.

Does the EyeSDN device need to be connected directly to the NTBA?

The device may be connected directly to the NTBA but may also be connected directly to a telephone or your telephone system.

Can the EyeSDN device be connected to my internal Fritz!Card and the S0 interface?

Yes, you may connect the device between your internal Fritz!Card and the NTBA connector.

How many devices can I connect to one computer?


You can connect up to eight EyeSDN USB-S0 or EyeSDN USB-A2 device to one computer, and can also use a USB hub. All of the recorded data can be managed from one software instance.


You can install up to four EyeSDN USB-4S devices into one computer. It is possible to use an USB hub for two EyeSDN USB-4S devices.


We recommend that only one E1 device be attached per computer, as when recording 30 channels the data quantity can accumulate very quickly. If the computer is suitably equipped and each E1 device has its own USB interface, then two or three devices may be connected to one computer. The EyeSDN USB-E1 devices should not be connected via a USB hub, as one device alone requires over 50% of the available data rate.

What do the "Layer 1 active, Layer 2 active and Layer 3 active" states mean on the EyeSDN USB-E1?

Layer 1 active = red LED

this means that a functioning connection to the nearest switching center has been established.

Layer 2 active = yellow LED

this means that an exchange of data packets is taking place through this connection and that the line is available for use.

Layer 3 active = green LED

this means that calls are taking place over this line. This could mean one call or up to 30 calls simultaneously.